During operation of fuel injectors with coil drive, because of electrical, magnetic, mechanical, and hydraulic tolerances, different chronological opening and closing responses of the individual injectors and thus variations in the respective injection volume occur. The relative injection volume differences from injector to injector increase as the injection times become shorter and shorter. When injection volumes are large, these relative volume differences are small and without practical significance. The development in the direction of smaller injection volumes and times, however, renders it no longer possible to disregard the influence of the relative volume differences. Therefore, it is of great importance to know the characteristic properties of a given fuel injector individually and precisely, so that these can be considered when driving the fuel injector.